Diaphragm electrolytic cells have been used widely in the production of chlorine and caustic from brine. It is conventional in such cells to employ elongated, hollow finger-shaped cathodes with graphite anodes interdigited between the cathodes. The asbestos diaphragm is customarily deposited in situ on the cathode so as to divide the interior of the cell into a catholyte and an anolyte compartment. Among recent developments have been new, long lasting metal anodes, along with preformed membranes made of polymeric materials which may be either semipermeable (allow only ions to permeate them) or hydraulically-permeable (allowing the electrolyte to permeate them). In spite of the increase of life of these preformed membranes, as well as a number of additional advantages, there is still the problem of fitting these membranes between the cathodes and the anodes in the cell to form fluid tight catholyte and anolyte compartments. These membranes must be fitted over either the anodes or the cathodes and do not naturally adhere to the electrodes as do the asbestos diaphragms which have, for the most part, been formed in situ on one electrode or the other.
As would be expected, those skilled in the art have sought an answer to this particular problem. U.S. Pat. No. 3,980,544 discloses complex clamping means, requiring major modifications in the electrolytic cells now in use. Any deviation of any of the metal clamp parts disclosed in this patent presents a possibility for a leak. U.S. Pat. No. 3,878,082 discloses and claims resilient means for holding the diaphragm in place, but does not detail how the open edges of the diaphragm or membrane sheet are to be sealed. U.S. Pat. No. 3,923,630 discloses a cylindrical, continuous sheet of preformed membrane positioned about a cylindrical electrode and held in place by being glued or sealed to upper and lower membrane supports. In actual practice, it is extremely difficult to completely seal the entire edge of these membrane sheets for the fifty or more electrodes included in each electrode section, and this task is multiplied many times when one considers that a large plant for producing chlorine and caustic may have several thousand electrodes.